1. Field
Embodiments of the invention relate to the field of computer networking; and more specifically, to shaping data traffic in a computer network.
2. Background
A modern metro area network 100 is composed of two types of networks: a core network 102 and one of more access networks 106. The core network 102 communicates data traffic from one or more service providers 104A-104N in order to provide services to one or more subscribers 108A-108M. Services supported by the core network 102 include, but are not limited to, (1) a branded service, such as a Voice over Internet Protocol (VoIP), from a branded service provider; (2) a licensed service, such as Video on Demand (VoD), through a licensed service provider and (3) traditional Internet access through an Internet Service Provider (ISP).
The core network supports a variety of protocols (Synchronous Optical Networking (SONET), Internet Protocol (IP), Packet over SONET (POS), Dense Wave Division Multiplexing (DWDM), OSPF, BGP, ISIS, etc.) using various types of equipment (core routers, SONET add-drop multiplexers (ADM), DWDM equipment, etc.). Furthermore, the core network communicates data traffic from the service providers 104A-104N to access network(s) 106 across link(s) 112. Link(s) 112 may be a single optical, copper or wireless link or may comprise several such optical, copper or wireless link(s).
On the other hand, the access network(s) 106 complements the core network 102 by aggregating the data traffic from the subscribers 108A-108M. Access network(s) 106 may support data traffic to and from a variety of types of subscribers 108A-108M, (e.g. residential; corporate, mobile, wireless, etc.). Although the access network(s) 106 may not comprise of each of the types of subscriber (residential, corporate, mobile, etc), access(s) network 106 will comprise at least one subscriber. Typically, access network(s) 106 supports thousands of subscribers 108A-108M. Access network(s) 106 aggregates data traffic from the subscribers over link(s) 112 connecting to the core network 102. Access networks support a variety of protocols (IP, Asynchronous Transfer Mode (ATM), Frame Relay, Ethernet, Digital Subscriber Line (DSL), Dynamic Host Configuration Protocol (DHCP), Point-to-Point Protocol (PPP), Point-to-Point Protocol over Ethernet (PPPoE), etc.) using various types of equipment (Edge router, Broadband Remote Access Servers (BRAS), Digital Subscriber Line Access Multiplexers (DSLAM), Switches, etc). The access network(s) 106 uses subscriber policy manager(s) 110 to set policies for individual ones and/or groups of subscribers. Policies stored in a subscriber policy manager(s) 110 allow subscribers access to different ones of the service providers 104A-N. Examples of subscriber policies are bandwidth limitations, traffic flow characteristics, amount of data, allowable services, etc.
Before discussing subscriber policies and the effect on services, it is worth noting that data traffic is transmitted in data packets. A data packet (also known as a “packet”) is a block of user data with necessary address and administration information attached, usually in a packet header and/or footer that allows the data network to deliver the data packet to the correct destination. Examples of data packets include, but are not limited to, IP packets, ATM cells, Ethernet frames, SONET frames and Frame Relay packets. Data packets are transmitted in a flow at a transmission rate. The transmission rate is determined by the packet size and the transmission gap (or “inter-packet gap”) between each packet. In addition, the transmission rate of data packets is dependent on the capacity of the network connection and processor capability of the transmitting device.
FIG. 2 represents the Open Systems Interconnect (OSI) model of a layered protocol stack for transmitting data packets 200. Each layer installs its own header in the data packet being transmitted to control the packet through the network. The physical layer (layer 1) 202 is used for the physical signaling. The next layer, data link layer (layer 2) 204, enables transferring of data between network entities. The network layer (layer 3) 206 contains information for transferring variable length data packet between one or more networks. For example, IP addresses are contained in the network layer 206, which allows network devices to route the data packet. Layer 4, the transport layer 208, provides transparent data transfer between end users. The session layer (layer 5) 210, provides the mechanism for managing the dialogue between end-user applications. The presentation layer (layer 6) 212 provides independence from difference in data representation (e.g. encryption, data encoding, etc.). The final layer is the application layer (layer 7) 212. The layer contains the actual data used by the application sending or receiving the packet. While most protocol stacks do not exactly follow the OSI model, it is commonly used to describe networks.
Returning to FIG. 1, bandwidth sensitive services, such as VoIP or VoD, require a dedicated bandwidth over link(s) 112 to properly operate. However, because each access network 106 can support thousands of subscribers, link(s) 112 can get overloaded and not provide enough bandwidth for these bandwidth sensitive services. Subsequently, the quality of these services degrades or becomes interrupted altogether. One solution to this problem is to enforce a Quality of Service (QoS) from the core 102 and/or access 106 networks. QoS allocates different bandwidth rates to different types of data traffic. For example, QoS can be set up to allocate a bandwidth of 20 Mbps for VoIP service over link(s) 112. In addition, QoS shapes the data traffic by re-transmitting the data traffic in a constant rate. However, for QoS to work properly, both the core and access networks must be set up to support the desired QoS policy.
Devices that solely perform QoS can be categorized, but not limited to, either traffic shapers or flow switches. A traffic shaper is a device that classifies a packet by deep packet inspection and transmits the packet based on pre-determined subscriber policies. Turning to FIG. 2, deep packet inspection examines the data contained in layers up to and including application layer 214 of each data packet 200 to determine what quality or service should be used for the packet. For example and by way of illustration, deep packet inspection matches the structure of the application layer data with potentially hundreds of known application data types. This allows a traffic shaper to finely tune the quality of service enforced. For example, a traffic shaper may identify control packets for an adaptable video conferencing protocol to configure the network for an optimal video conferencing rate.
Although existing traffic shapers are subscriber aware, these traffic shapers only enforce pre-determined subscriber policies. That is subscribers policies are set by the operator of the traffic shaper and do not change until the operator modifies the subscriber policies. This does not allow subscriber policies to change in real-time based on existing network conditions. Furthermore, existing traffic shapers cannot handle the high volume of data traffic that cross the core 102 and access 116 networks.
On the other hand, flow switches are network devices that transmit data packets in connected flows, instead of discrete packets. Flow switches operate on groups of similar packets to provide QoS for an application. However, flow switches have limited data traffic processing capability, are not subscriber aware, perform limited or no deep packet inspection, and cannot update subscriber policies in real-time.